1. Field of the Invention
The present invention relates to a method and to circuit arrangements for level monitoring for a data signal.
2. Description of the Prior Art
It is frequently necessary to monitor the receiving level in digital data transmission. By so doing, one can determine whether a line is occupied by other subscribers or is free. A specific starting procedure in which only the subscriber side or the exchange side, respectively, transmit in succession is likewise frequently defined for a call setup. When switching, the level shut-off must first be monitored and recognized and the level cut in must be monitored and recognized later, for example, after the recognition of a prompter signal. The fault-free function must thereby be guaranteed for a great level range, since the level of the received signal is dependent on an extremely-different line length. Leveling monitoring disclosed up to now proceed on the basis of a fixed comparison value, as a result thereof a reliable operation is no longer possible given high-disturbed or noise-infested signals.